Apparatus for coating and curing epoxy resin on sheets



sept. 16, 1969 N, K, KLEBANQW- ET AL 3,467,060

APPARATUS FOR COATING AND CURING EPOXY RESIN ON SHEETS Filed Oct. 19.1967 INVENTUM Noe/74 4T isa/wou 0 N 54661? BY M l Amp/V67 d .lu HP aff#4 United States Patent O 3,467,060 APPARATUS FOR COATING AND CURINGEPOXY RESIN ON SHEETS Norman K. Klebanow, Yonkers, and Dan Sager,Hartsdale, N.Y., assignors, by mesne assignments, to The Longacre Press,Inc., New Rochelle, N.Y., a corporation of New York Filed Oct. 19, 1967,Ser. No. 676,504 Int. Cl. B05c 11/00, 11/06, 1/00 U.S. Cl. 118-58 5Claims ABSTRACT 0F THE DISCLOSURE A technique for epoxy coating paperand cloth surfaces such as dust jackets, book covers, and the like,wherein the printed sheets are fed onto a continuous conveyor andadvanced thereby under an engraved roll having an epoxy solution appliedthereto, the roll laying down a raised pattern of the solution on theprinted face of the sheets, which pattern levels off and merges to forman evenly distributed wet coating, the Wet coated sheets thereafterbeing dried and cured.

This invention relates generally to paper and cloth coating techniques,and more particularly to apparatus for applying a clear epoxy coating toa dust jacket or to a book cover.

Hard-cover books are generally provided with a removable paper dustjacket which serves to protect the relatively expensive stiff binding.While the dust jacket may ultimately be discarded, its form andappearance are commercially significant, for when the book is displayedit is only the dust jacket which is visible to the potential purchaser.An attractive jacket constitutes an important factor in inducing a sale;consequently, book publishers exercise great care in jacket design.

In recent years, the sale of low-cost paperback books has risen to suchdimensions that one often speaks of the paperback revolution. Thedurability of such books depends to a large degree on the quality andstrength of the soft cover, whereas the salability of these books isgreatly influenced by the appearance of the printed soft cover, for nodust jacket is provided.

Paper of the type ordinarily used for dust jackets or for paperbackcovers has a somewhat dull finish. Also, the surface of such paper iseasily sculfed or otherwise mutilated. It has therefore been thepractice to coat the printed face of the paper with a clear top coating,such as oleo-resinous varnish which not only improves its scuifresistance, but also imparts some degree of luster or gloss thereto.However, varnish coatings have a relatively short life and theyadversely affect the color print. The main virtue of varnish coatings isthat they can be applied at low cost. Also, varnish coatings whether ofthe press or spirit type tend to yellow with age and they impart onlylimited scut resistance to the paper or cloth base.

Attempts have also been made to used cellulosic rather than varnishcoatings, but these plastic coatings have certain drawbacks, for theyare necessarily thin and do not give the paper good body. Moreover, notonly do cellulose acetate and other cellulosic coatings yellow with age,but the plasticizers commonly used therewith tend either to evaporate orto migrate into the paper, thereby embrittling the coating and furtherdegrading this product.

An alternative approach which produces a high-quality product, is tobond a transparent plastic film to the paper jacket or cover. While theresultant laminated cover has excellent scul resistance and goodappearance, there are a number of serious practical disadvantages to thetechniques involved. First, there is the matter of cost, for plasticTice film of good quality, such as vinyl or Mylar, is expensive, in theorder of one dollar a pound and higher. Even the clear adhesive forbonding the film to the paper is costly, the adhesive running as much asfty cents a pound.

Also, the laminating technique is difficult, time-consuming and costlyfrom the labor standpoint, for the paper sheets must be fed sequentiallyinto combining rolls where they are laminated with liquid adhesive to acontinuous web of film, the combination then being wound on a take-uproll. In some cases, several hours are necessary to allow the adhesiveto dry, after which the combined web is unwound and the laminated sheetscut therefrom.

Accordingly, it is the main object of this invention to provide atechnique for applying an epoxy coating onto a paper cover jacket orother printed paper or cloth surface, which coating imparts a highdegree of scud resistance to the surface, the resultant product havinggood body and an attractive appearance.

A salient feature of the invention is that the technique is comparablein cost to conventional paper-varnishing, and yet the product iscomparable in quality to that heretofore attained only by plastic filmlamination. Also the epoxy coating may serve to enhance the gloss of thepaper, although it is possible by the use of additives to reduce theglossiness of the surface when a less shiny effect is required.

More specifically, it is an object of the invention to provide atechnique for applying a relatively heavy and uniform coating of anepoxy solution onto sequentially fed sheets of paper, the wet coatingbeing quickly dried and cured to form a clear, smooth adherent film onthe paper which is highly flexible and crack-free.

Briey stated, these objects are accomplished in a system wherein sheetsof paper or other materials are fed in succession onto a conveyor beltwhich conducts them under an engraved roller to which is applied anepoxy solution, the solution being picked up by the roller and beinglaid down on the sheet in a raised, wet pattern pattern whichcomplements the engraved roll pattern, the wet pattern leveling off andmerging to form a uniform coating on the sheet, the wet, coated sheetsthen entering a treatment tunnel wherein the coating is subjected toinfra-red radiation or heated air to effect drying and curing thereof,after which the coated sheets are collected in a jogger.

For a better understanding of the invention, as well as other objectsand further features thereof, references is made to the followingdetailed description to be read in conjunction with the accompanyingdrawing, wherein:

FIG. 1 schematically shows a system in accordance with the invention;

FIG. 2 separately shows the applicator stage of the system;

FIG. 3 is a View of the profile of the engraved roller; and

FIG. 4 is a section taken through the epoxy-coated paper.

The term epoxy resins covers a group of resins ranging from brittlesolids to low-viscosity liquids made by the reaction of bisphenol andepichlorohydrin. The epoxies are linear copolymers that can cross-linkto form thermosetting resins by reaction with amine type compounds. Themanufacture of surface coatings was one of the first and continues asone of the largest uses of epoxy resins, for these coatings combine theproperties of toughness, exibility, adhesion and chemical resistance toa degree not found in other coating materials.

The present invention is concerned with epoxy resins used in solutionwith certain compatible phenolic or urea resins. These blends areheat-convertible and form copolymers or condensates to produce extremelytough, durable and liexible lms with excellent resistance to solventsand chemicals. While it has been known to use such resins as liningmaterials for tanks and cans as well as hardware finishes, it has notheretofore been feasible to coat paper therewith. Spraying and dippingtechniques, while suitable for linings and finishes, are not feasiblewith paper or other sheets. While the present invention will bedescribed in connection with paper sheets, it is to be understood thatit is equally applicable to sheets formed of woven or nonwoven materialswhich are printable.

Application of an organic coating to sheets resolves itself principallyinto a method of applying a smooth, wet film of a uniform, controlledthickness to a web or sheet of the paper or other material. Variousmachines are currently available for this purpose in connection withvinyl dispersions and other organic materials, including thereverse-roll coater and the contracoater, both of which involve the useof a metering or doctor roll whose position with respect to a transferroll determines the thickness of the liquid applied to the sheet.

Conventional applicators are not suitable for liquid epoxies, for theliquid when exposed, has a relatively short life, and with conventionalcoaters there is a buildup of liquid at the metering roll, as a resultof which some of the liquid is stale and .undergoes a reaction beforereaching the paper. Moreover, it is difficult with conventional rollercoatings to control the thickness of viscous epoxy solutions applied topaper sheets.

Referring now to FIG. 1, there is shown a system in accordance with theinvention, comprising a paper feeder stage 10, a liquid applicator stage11, a drying and curing stage 12, and an output stage 13. In the feederstage, a stack of paper sheets 14 is supported on a platform and istransferred one by one from the stack onto the input feed of an endlessconveyor belt 15, formed by a broad web, by means of a feeder mechanism16. The web may be of fabric screen or any other suitable design. Thefeeder mechanism may be of the standard vacuum or mechanical fingertype. The paper sheets are printed with an appropriate cover design. Inpractice, each sheet may contain several design impressions and afterthe sheets are epoxy-coated, they are cut into individual soft coverdust jackets or other individual units.

Conveyor belt 15 is supported between end rollers 17 and 18, roller 18being driven by a motor 19 whereby the sheets 14 fed thereon aresequentially advanced toward an applicator roll 20 which is supportedfor rotation above the belt and is transversely disposed with respectthereto. The rate at which the feeder mechanism places sheets on theconveyor belt relative to the speed of the moving belt is made such thatsheets 14 are marginally overlapped rather than separated on the belt.This is important, for by such overlap the engraved roll which applies asolution to the face of the sheets effectively sees an uninterruptedpaper surface, as a consequence of which no liquid is applied to thebelt surface, and the belt remains clean. In a practical embodiment, abelt speed of 10,000 feet per hour has been used, although the inventionis by no means limited to this particular rate.

As shown separately in FIGS. 2 and 3, the surface of the roll except forthe end portions thereof, is engraved to define a series of equi-spacedannular channels 20A, 20B, 20C, etc., thereacross. This engraving may beeffected by known mechanical or chemical etching techniques in a steelroll or a roll of any other suitable material non-reactive with thesolution being used.

The epoxy solution preferably is applied to roll 20 by means of afountain trough 21, the trough being provided with a doctoi blade 21Awhich engages the periphery of the roll so that the solution is admittedonly into the engraved annular channels and not on the surface of roll20. The trough extends across the engraved portions of the roll and alittle beyond at each end of the engraved portion, so that the ends ofthe trough overlap the non- 4 engraved portions of the roll, therebypreventing leakage of the solution. The position of the doctor blade 21Ais adjacent the point at which the advancing paper enters the nip of theengraved roll 20, so that the solution has a very limited exposurebefore being laid down on the paper surface, thereby minimizing dryingeffects.

The epoxy solution is dispensed into the trough from a suitable pumpmetering system 22, the amount of solution fed into the trough beingregulated as a function of epoxy take-up by the paper sheets, so thatonly a small reservoir is built up in the trough, which reservoir iscontinuously being depleted in the course of coating and is continuouslybeing replenished. This is important in order to avoid an excessivebuild-up of solution in the reservoir.

Alternatively, the epoxy solution may simply be poured onto theadvancing sheets at a point adjacent the nip of the roll 20, the nipacting to spread the solution across the roll. Dams may be installed atthe ends of the roll to prevent spillage of the solution.

The solution enters the channels on the roll and is transferred from thechannels. to the printed face of the sheets passing thereunder. Roll 20is an idler and operates in conjunction with a platen roll 23 disposedbelow the belt, such that when a sheet enters the nip of roll 20,sufiicient compression of the sheet and of the belt interposed betweenrolls 20 and 23 occurs to cause the exposed roll to turn and to applythe resin solution to the paper. Alternatively, the engraved roll may bedriven at a rate in keeping with the belt movement.

The solution is applied to the face of the paper in the form of parallelstreams corresponding to the configuration of the channels. However, theviscosity of the solution is such that the streams level and merge toform a uniformly-distributed wet coating on the paper surface beforedrying and curing takes place. The invention is not limited to any oneform of engraved pattern, and includes various other patterns, such aswaffle-like or spiral conligurations.

The wet coated sheets on the conveyor belt 15 are transferred to anelongated conveyor 24 constituted by continuous bands in spaced parallelrelation. Conveyor 24 advances the wet-coated sheets at a slightlygreater speed than conveyor 15, thereby causing the sheets to separate.The separate sheets are conveyed through a tunnel 25 wherein the wetcoating is subjected to infrared radiation, circulating heated air, orother curing means which acts to dry and cure the epoxy to produce anadherent film on the sheets.

The thickness of the coating depends primarily on the depth of theengraving, and in practice this may be made to range from .1 mil to anygreater thickness. As shown in FIG. 4, each dried and cured sheet isconstituted by a paper base P and a uniform epoxy film E adhered to theprinted face thereof.

The sheets from tunnel 25 are transferred to an output stage 26 which ispreferably in the form of an automatic jogger or vibrator which servesto restack the sheets and to place them in condition for efficienthandling or further processing.

As pointed out previously, the chemical nature of the epoxy solutionmust be such that it has a satisfactory pot life, proper viscosity, anda solvent system which will avoid drying of the solution on the engravedroll.

While there has been shown and described a preferred embodiment of theinvention, it will be appreciated that many changes and modificationsmay be made therein without, however, departing from the essentialspirit of the invention.

Thus, while the applicator has been described as it operates inconnection with epoxy solutions, it will be appreciated that it can alsobe used to advantage with other solutions for coating sheets which arenot in wet form, such as vinyl dispersions, organosols and plastisols.

Another approach to applying the epoxy solution to the surface of thesheets is by the use of an offset press arrangement including a threeroller unit constituted by an impression cylinder which coacts with ablanket cylinder, this in turn engaging a plate cylinder. Operating inconjunction with the plate cylinder is a fountain vcontaining thesolution to be applied. Rotating within the fountain is a metal meteringroll, preferably engraved in the manner previously described, whichpicks up a controlled amount of the solution and applies it to a rubbertransfer roll, the latter roll engaging the surface of the platecylinder, which in turn applies the liquid coating to the blanketcylinder.

The paper sheets are fed between the impression cylinder and the blanketcylinder in overlapping relationship, as in the embodiment previouslydescribed, the coated sheets then being fed into the curing and dryingzone. Alternatively one may dispense with the plate cylinder and applythe solution from the transfer roll directly onto the blanket roll. Thethickness of the coating depends on the viscosity of the solution andthe roller speed, as well as the depth of the engraving on the meteringroll.

What we claim is:

1. A system for applying a wet solution to the surface of sheets, whichsolution is of a composition which, when dried, forms an adherentscafi-resistant protective film; said system comprising:

(A) an applicator stage including a conveyor operating at apredetermined speed, a roll supported above ysaid conveyor to engage thesurface of sheets fed therebetween, and means to apply said solution tosaid roll to coat same whereby said roll in turn applies said solutionto said surface;

(B) a feeding stage provided with a stack of sheets and including meansto remove said sheets sequentially from the stack and to transfer themto the applicator conveyor at a rate relative to the speed thereof atwhich said sheets are caused to marginally overlap whereby said rolleffectively sees an uninterrupted surface and applies said solutionthereto;

(C) a drying stage coupled to the output of said applicator stage andincluding a conveyor operating at a speed slightly greater than saidpredetermined speed to cause said sheets conveyed thereby to separate,land means to subject said separated sheets to heat to dry said solutionthereon; and

(D) a collector stage coupled to the output of said drying stage toreceive said separated sheets one above the other to form a stackthereof.

2. A system, as set forth in claim 1, wherein said solution has apredetermined viscosity and said roll has a pattern of indentationsthereon to receive said solution, the roll forming a correspondingraised pattern of the solution on 'the surface of the sheets engagedthereby, the viscosity of the solution relative to the conveyor speed insaid applicator stage being such that the solution levels off on thesurface to form a wet coating which becomes uniform before the sheetsenter the drying stage.

3. A system as set forth in claim 2, wherein said means to apply saidsolution to said engraved roll is constituted by a trough having adoctor blade engaging the surface of the roll.

4. A system as set forth in claim 3, wherein said engraved roll hasnon-engraved end portions and said trough overlaps said non-engravedportions to prevent leakage of the solution.

5. A system as set forth in claim 3, wherein said solution is dispensedinto said trough by a metering pump which is regulated to maintain asubstantially level reservoir in said trough.

References Cited UNITED STATES PATENTS 1,606,554 11/ 1926 Wycherley etal. 118-236 XR FOREIGN PATENTS 268,545 5/1950 Switzerland.

WALTER A. SCHEEL, Primary Examiner R. I. SMITH, Assistant Examiner U.S.Cl. X.R. 118-236

